Study On Potential Technology For Nitrogen And Phosphorus Removal From Large Scale Swine Wastewater

With the booming development of livestock industry, the discharge of large scale swine wastewater had caused severe environment contamination in Chinese rural area and suburbs. The large amount of wastewater containing COD, ammonia nitrogen and phosphorus in high concentration was poured into water body, caused eutrophication and groundwater pollution. Therefore, it’s necessary to treat swine wastewater before discharge. Nowadays, conventional anaerobic-aerobic treatment process and SBR treatment process were applied to swine wastewater treatment, which were possessed of low nitrogen and phosphorus removal efficiency, high operating costs and great nutrient losses. Aiming at overcoming these drawbacks, a treatment process consisted of UASB, step-fed sequencing batch reactor (SFSBR) and denitrifying phosphorus removal SBR was built. The three reactors could achieve COD removal, nitrogen removal and phosphorus removal respectively. The main research achievements are as follows:A pilot engineering consisted of UASB, SFSBR and magnesium ammonium phosphate precipitation reactor (MAP) was constructed to treat swine wastewater at first. The effluent quality was superior to Discharge standard of pollutants for livestock and poultry breeding (GB18596-2001), mass concentration of COD, TN, NH4+-N, TP and SS was not higher than135,116,43,7.3and50mg-L"1respectively. The process developed was reliable, kept self-balance of carbon source and alkalinity, and realized high nutrient recovery efficiency. What’s more, the operating cost was equal to traditional anaerobic-aerobic treatment process. However, the MAP reactor was difficult to operate for its complex operating parameter, relatively high operating cost and low precipitation purity. So it’s necessary to develop a biological phosphorus removal process to treat UASB-SFSBR effluent.After a preliminary analysis of UASB-SFSBR effluent, it was found that mass concentration of NO3--N, NO2--N and TP was4.76±0.43mg·L-1,49.93±9.83mg·L-1and39.64±4.84mg·L-1, so denitrifying phosphorus removal process could be available for the effluent. A laboratory SBR was constructed to treat synthetic UASB-SFSBR effluent. The SBR anaerobic influent contained NaAc (COD), while the anoxic influent contained phosphate and electron acceptor such as nitrate and nitrite. The denitrifying phosphorus accumulation organisms (DNPAOs) were sucessfully enriched by this reactor. By futher experiments, it was discovered that the carbon sources utilization ratios of DNPAOs were from0.25to0.3, the removal ratio of nitrite to phosphorus was0.90±0.08, while the removal ratio of nitrate to phosphorus was0.67±0.04. When the anaerobic influent COD concentration was1650mg·L-1, the anoxic influent NO3--N, NO2--N and PO43--P concentration was5,70and30mg-L-1respectively, both the effluent NO3--N and NO2--N concentration were0, and the PO43--P concentration was below1.0mg·L-1. The results showed that the treatment process was available.The treatment process achieved "one-carbon dual-use" that solved carbon source competion between denitrifying bacteria and PAOs in traditional biological nitrogen and phosphorus removal technology, it possessed high treatment efficiency and low operating costs. So the treatment process could provide high value of application and dissemination and be fit for the treatment of large scale swine wastewater in China.